way to close for mh but floros dont give off heat and the spectrum of light is better if the plant is as close as possable i'm useing a 125 watt envirolite cfl and 4 four foot floro tubes if you dont keep floros close to your plants they will stretch to the light and be weak and stringy closer lights will also increase yeild and give you better buds and stronger plants at least thats what works for me good luck hope this helps